RFID transponders, also known as RFID tags, may be affixed to items for the purpose of making those items identifiable and/or trackable. RFID transponders can be small, inexpensive, and unobtrusive, making it feasible to affix them by a variety of means, including incorporation into stick-on labels, or encapsulation for the purpose of implanting under skin or embedding in the interior of an item. Examples of items to which RFID transponders can be affixed include pieces of merchandise in a store, palettes of goods in shipment, vehicles on a toll road, passports, books in a library, and individual animals.
In RFID systems, an RFID reader emits a radio signal to which an RFID transponder responds. The response is detected, or read, by the RFID reader. The response includes a transponder identifier, called a tag ID, and may convey additional data about an item associated with the transponder. The reader forwards the data from the transponder to another element of the RFID system which may filter and aggregate the data. Ultimately, the data arrives at a backend system for processing. The backend system supports software applications that utilize the RFID data for whatever purpose is served by the RFID system.
A multiplicity of transponders may exist within range of the RFID reader. Each transponder may respond to the signal emitted by the RFID reader. Because transponders may enter and exit the range of the RFID reader, the RFID reader uses its emitted radio signal to periodically interrogate, or sample, the transponders within its range. The RFID reader may sequentially interrogate every transponder in its range in a given sample period (bulk reading), or it may interrogate specific transponders at a particular time. Transponders that remain in the range of the RFID reader from one sample period to another may, if bulk read, create duplicate, redundant information in the RFID system.
The RFID reader may be one of many in the RFID system. As data from a multiplicity of RFID readers, each conveying data from a multiplicity of RFID transponders in its range, is funneled upward through middleware to the backend system, the volume of data traffic may tax the capacity of the interconnections and storage resources in the RFID system. It is, thus, desirable to filter from the data traffic duplicate or redundant information.